fix(ui): drain React 19 scheduler before jsdom teardown in App.cloud-shell test

CI's "Client Tests" job failed with an unhandled `ReferenceError: window is
not defined` originating in `App.cloud-shell.test.tsx`. All 835 tests
passed, but a React 19 scheduler callback queued via `setImmediate` fired
after the per-file jsdom environment was torn down, after which `window`
no longer exists. Add an `afterAll` that awaits a `setImmediate` tick so
the scheduler's pending work runs while `window` is still alive, and an
`afterEach` that calls testing-library's `cleanup` to unmount any
straggler trees before the drain.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Shaw

packages/ui/src/App.cloud-shell.test.tsx

@@ -14,8 +14,22 @@
 import { readFileSync } from "node:fs";
 import { resolve } from "node:path";
 
-import { render } from "@testing-library/react";
-import { beforeAll, describe, expect, it, vi } from "vitest";
+import { cleanup, render } from "@testing-library/react";
+import { afterAll, afterEach, beforeAll, describe, expect, it, vi } from "vitest";
+
+afterEach(() => {
+  cleanup();
+});
+
+// React 19's scheduler can post a `setImmediate` callback that runs AFTER
+// the test file completes but while Vitest is tearing down the per-file
+// jsdom environment, throwing `ReferenceError: window is not defined`
+// from react-dom-client.development.js. Drain the macrotask queue before
+// the environment is unwound so any pending scheduler work runs while
+// `window` still exists.
+afterAll(async () => {
+  await new Promise<void>((resolve) => setImmediate(resolve));
+});
 
 beforeAll(() => {
   if (typeof window.matchMedia !== "function") {